Year	% of land area
1961	2.1174972138194557
1962	2.1652603088680147
1963	2.1174972138194557
1964	2.1174972138194557
1965	2.1015761821366024
1966	2.101576182136603
1967	2.069734118770896
1968	1.8946027702595127
1969	1.926444833625219
1970	1.9662474128323515
1971	1.9742079286737781
1972	2.021971023722337
1973	2.021971023722337
1974	2.021971023722337
1975	2.1334182455023085
1976	2.213023403916574
1977	2.324470625696545
1978	2.4199968157936635
1979	2.443878363317943
1980	2.4518388791593697
1981	2.5473650692564878
1982	2.6428912593536062
1983	2.7479700684604365
1984	2.833943639547843
1985	2.993153956376373
1986	2.9995223690495143
1987	3.1157459003343417
1988	3.279732526667728
1989	3.462824391020538
1990	3.6299952236904955
1991	3.7770849571317227
1992	3.6554949337490257
1993	3.565081839438815
1994	3.474668745128605
1995	3.3219017926734216
1996	3.2314886983632114
1997	3.1254871395167574
1998	3.05066250974279
1999	2.996102883865939
2000	2.8698363211223694
2001	2.795011691348402
2002	2.6890101325019486
2003	2.6141855027279814
2004	2.523772408417771
2005	2.4333593141075602
2006	2.333593141075604
2007	2.2525331254871395
2008	2.162120031176929
2009	2.034294621979735
2010	2.1356196414653157
2011	2.219797349961029
2012	2.3507404520654713
2013	2.434918160561185
2014	2.5502727981293845
2015	2.6572096648480126
2016	2.5745908028059237
2017	2.493915756630265
2018	2.4110764430577225
2019	2.416380655226209
2020	2.43198127925117
2021	2.43198127925117